import requests

json_data = requests.get(url='https://cn.bing.com/hp/api/model?mkt=zh-CN').json()
pic_url = 'https://s.cn.bing.net' + json_data['MediaContents'][0]['ImageContent']['Image']['Wallpaper']
print(pic_url)

img_data = requests.get(pic_url).content
with open('biying.jpg', 'wb') as f:
    f.write(img_data)